How Much Does Endpoint Security Slow Down a Computer?

Endpoint security software slows a computer mainly when it scans files, inspects processes and syncs updates. The amount depends on the product, the machine and the workload, so no single number is trustworthy. Measure your own baseline before and after, and fix hotspots without turning protection off.

Where does the cost come from?

NIST SP 800-53 control SI-3 on malicious code protection describes the work. It asks for protection at system entry and exit points, automatic updates, periodic scans of the system and real-time scans of files from external sources as they are downloaded, opened or executed. Each of those uses resources:

• Real-time scanning adds a check every time a file is opened or executed. Workloads that touch many small files, like builds and package installs, pay the most.
• Full scans read the whole disk and can compete with the user for storage and CPU.
• Behavior monitoring hooks into process and network activity, which costs a small amount on every action.
• Updates and telemetry use network and brief CPU spikes.

NIST SP 800-83 Rev. 1, on malware incident prevention, calls malware the most common external threat to most hosts. That is the reason the cost is usually worth paying, and the reason to manage it rather than switch the tool off.

Why do published numbers disagree?

Because performance is a property of a combination: product, version, configuration, hardware and what the user does. A developer compiling code and a receptionist using a browser experience the same agent very differently. We are not citing a percentage here because a general figure would mislead you.

A constructed example

A software team reports that builds got slower after a new endpoint agent rollout. Instead of arguing, an engineer times the same clean build on three identical laptops: one without the agent in a test group, one with the default policy, one with a tuned policy.

The default-policy laptop shows the largest delay, and tracing shows the real-time scanner inspecting the build output folder thousands of times. The security team adds a narrow, documented exclusion for that folder, and in return enables stronger controls on the download directory and on execution from user-writable paths. Build time recovers most of the loss, and the team keeps a written record of why the exception exists.

What are the risks of exclusions?

Every exclusion is a place where the scanner does not look, and attackers can place tools in excluded locations. So treat an exclusion like a firewall rule: scope it narrowly, give it an owner, record the reason and set a review date. SI-3 also asks organizations to address false positives, which is a related tuning problem.

How to check or apply this

1. Pick three or four representative tasks per user group: boot, login, a large file copy, a typical build, opening large documents.
2. Time them on a machine with and without the agent, or with default and tuned settings. Repeat several times and compare averages.
3. Use the operating system's monitoring tools to see which processes use CPU, disk and memory during slow moments.
4. Schedule full scans for idle hours and stagger them so every machine does not scan at once.
5. Add exclusions only for specific paths or processes with evidence of cost, and document each.
6. Re-test after every major agent update, since behavior changes.
7. Collect complaints from users in one place, and tie each to a measurement so fixes are based on data.

Quick check

Sources

• NIST SP 800-53 Rev. 5 control catalog, OSCAL JSON from NIST (SI-3)
• NIST SP 800-83 Rev. 1, Guide to Malware Incident Prevention and Handling for Desktops and Laptops

Last reviewed: 18 October 2026.